Temperature responsive system



Sept. 11, 1951 R. AMSLER TEMPERATURE RESPONSIVE SYSTEM 5 a :0 l2 Lsp resist Temp. resp.

SLER MM ROBER W i;

INVENTOR TTORNEYS Patented Sept. 11, 1951 2,567,756 TEMPERATURE RESPONSIVE SYSTEM Robert Amsler, Zug, Switzerland, assignor to .Landis & Gyr, A. G., a body corporate of Switzerland Original application April 28, 1944, Serial No. 533,122. Divided and this application February 10, 1951, Serial No. 210,362. In Switzerland May 17, 1943 scams. 73-362) This application is a division of my application Serial No. 533,122, filed April 28, 1944.

The invention refers to temperature regulators which use a temperature dependent resistance as a sensitive member. Sensitive members of this nature are termed resistance thermometers and are useful for controlling a suitable operating instrument, either in bridge connection or directly as a series resistance. As operating instruments, may be mentioned either contact galvanometers, difierential relays or Ferraris contact wattmeters.

With the known embodiments of such temperature regulators, extraordinarily sensitive regulating instruments are necessary, since the metals used in practice for the resistance thermometers have only comparatively small temperature coefiicients and thus the resistances of the resistance thermometers only vary within narrow limits.

The present invention comprises an electric temperature regulator comprising an operating instrument having one or more coils and serving to control heating means whereby the temperature of a system is regulated, one of said coils being connected in series with a temperature feeler comprising at least one temperature-sensitive resistance, at least one additional temperature-sensitive resistance being connected in the circuit of said coil, the response of said additional temperature-sensitive resistance to variations in current through said temperature feeler being such as to increase the magnitude of said variations in the said coil of the operating instrument.

The accompanying drawings show diagrammatically by way of example several embodiments of the invention, in which:

Figure 1 shows the connection of a resistance thermometer hitherto usual while Figure '2 shows one specific form of the invention claimed in the application of which this is a division, this figure showing a resistance thermometer with thermal amplification,

Figure 3 represents by means of graphs the improvement attainable by the use of thermal amplification with a resistance thermometer,

Figures 4 and 5 show modifications of resistance thermometers with thermal amplification.

The following description refers to the use as operating or responding instrument of a differential relay or a galvanometer, but a Ferraris contact watt-meter 'may be equally well used.

In Figure 1 there is shown in principle the usual arrangement of the temperature sensitive member or feeler I in series with coil 2 of the operating or responding instrument, hereinafter referred to as the operating instrument. Any variation of temperature at sensitive member I effects a change of its resistance and consequently a variation of current. The variation of current obtained at the sensitive member or feeler I for a particular temperature variation is all the greater, the greater the ratio of feeler resistance to coil resistance of the operating instrument. As the feeler resistance there can be employed any material having as large a temperature coeflicient as possible which is positive, as for example with metals, or negative as for example with carbon or electronic semiconductors. In Figure 3 the graph a represents the percentage increase of current Jsp for an increase of feeler resistance by 10% as a function of the ratio of energy Lt consumed in the feeler resistance to the energy Li consumed in the coil of the operating instrument.

The principle of the thermal amplifier is shown in Figure 2. It consists in a temperature-dependent resistance 3, e. g. a metal filament incandescent lamp connected in parallel with coil 2 of the operating instrument. The'method of operation of this arrangement is as follows: If the resistance of ieeler I increases, the current falls in coil 2 and in lamp 3. Consequently the temperature of the incandescent filament falls and with it the resistance of the incandescent filament, so that now the current flowing through temperature feeler I is difi'erently distributed, more flowing through the temperature-dependent resistance 3 and less through coil 2 of the operating instrument. Thus, therefore, the original variation of current in coil 2 of the operating instrument is amplified. In consequence of the variation in resistance of lamp 3, a greater total current then flows than when the resistance remains constant, which again has as a, result that the drop in potential at the temperature feeler is greater and thus the coil current is again reduced.

By connecting in the temperature-dependent resistance 3, however, the energy consumed in the temperature feeler l is increased. If the arrangement is to present any advantage, the relative amplification must be greater than the effect which would be attained with like energy consumption in the feeler without thermal amplification. A comparison of the two arrangements has thus to take place based on a like ratio of the energy consumption in the feele'r to the energy consumption in the coil.

In Figure 3, the graph b shows such a comparison, using a metal filament incandescent lamp as the thermal amplifier, with a filament temperature of the order of 500 C. and a ratio of between coil resistance and lamp resistance. The course of this curve during which an increase of is to be assumed in the feeler resistance, shows that, as the ratio of feeler output to coil output increases, the percentage change of current Jsp increases rapidly to high magnitudes. The improvement J,,, (Curve b) J (Curve a) obtained by means of the thermal amplifier, is represented in Figure 3 by curve 0, which expresses the resulting amplification V in percentage terms on the right hand scale. From this it is evident that, in the present example, an amplification of at least 18% is obtained. A

A similar amplification effect may be attained if a temperature-dependent resistance having a negative temperature coefiicient is connected in series with the temperature feeler and coil of the operating instrument. This particular form of the invention is claimed in this application. Since the amplifier operates in air and is cooled by the air, its temperature variation may be comparatively great for a particular current variation, thereby its resistance also varies greatly and a considerable amplification efiect is attained.

The thermal amplification arrangement described has the further disadvantage of dependence on temperature, since it is exposed to the variable temperature of the surroundings. This could be obviated by mounting the amplifier in a housing of constant temperature. Much simpler than this, however, is the use of a second similar amplifier in the circuit of the second coil of the difierential relay. The two amplifiers then operate in opposition to each other and the dependence on temperature is thereby nullified. The arrangement above described has, however, a further advantage. It is known that in any temperature regulator, of which a high degree of accuracy is required, a resetting or calibrating device is necessary. This eiiects a temporary displacement of the regulated or standard value to which the device has been set, which displacement disappears again after a correction has been made of the regulated temperature. A resetting device can be introduced into the above described arrangement in a very simple manner. If the resistance acting as the thermal amplifier be heated by separate heating winding there results a variation of the coil current which is equivalent to a displacement of the regulated or standard value. If the heating is oil, then this displacement disappears again. It is therefore only necessary for this heating winding to be switched in and out each time by a contactor worked by the operating instrument in order to obtain the desired resetting. The operating instrument is thus brought back prematurely by the displacement of the regulated or standard value due to the heating of the thermal amplifier and switches its contactor out, before this would take place by. the temperature variation of the medium regulated. There is obtained in thisway a rigid resetting for an Open/Closed regulator and an elastic one for a progressive H regulator. The magnitude of the resetting is given by the heat capacity of the thermal amplifier and the period of resetting by the time of cooling thereof. These factors can be varied so that the regulator can be adapted to any purpose.

Figure 4 represents an arrangement according to the invention, in which I is the temperature feeler having a positive temperature coefficient which is in series with coil 2 of the operating instrument and temperature-dependent resistance 3 referred to as the thermal amplifier and having a negative temperature coefiicient. Resistance 3 can be heated by the heating winding 4 acting as a resetting devic which can be placed on potential through a contactor 6 worked by the operating instrument. The second coil 2| of the operating instrument is in series with an adjustable resistance 5 serving for adjusting the desired regulated or standard temperature and with the thermal amplifier 3! which, on its part, can be heated by the heating winding 4| that is also placed on potential by contactor 6. Furthermore, a regulating member I for controlling a heating system for example can be actuated in the desired direction by contactor 6 worked by the operating instrument.

Figure 5 also shows an arrangement like that of Figure 4 but the thermal amplifiers 3 and 3| have positive and the thermal amplifiers 8 and 8! negative temperature coefficients. The method of operation of these arrangements is easily understandable from the description of the method of working of the fundamental arrangement according to Figure 2.

The regulating arrangement above described has various possibilities of use. Thus for example, a temperature can be kept constant, either by off/0n regulation with rigid resetting or by progressive regulation with elastic resetting. On the other hand, a regulated temperature can be shifted thereby in accordance with a second temperature, a second temperature feeler being introduced instead of the adjusting resistance 5.

What is claimed is:

1. A temperature responsive system comprising a temperature responsive feeler resistor exposed to a temperature to be measured or controlled, a current responsive device having an operating coil, an additional temperature responsive resistor, means for connecting said two resistors and coil in series across a substantially constant source of potential, said feeler resistor and additional resistor having respectively positive and negative temperature coefficients, said feeler resistor being the only resistor subject to temperature to be measured or controlled with the additional resistor not being subject to the temperature being measured or controlled and said two temperature coeflicients having such relative magnitudes that under operating conditions the percentage change of feeler resistance for a given change of feeler temperature is greater than the resulting percentage change of resistance of said additional resistor whereby when said feeler resistor changes its resistance in response to a temperature change, the current through the additional resistor and coil is varied in an amplified manner and the movable element has a greater movement for a predetermined feeler temperature change in said system than in a system not having the additional resistor. 2. A temperature responsive system comprising a temperature feeler resistor exposed to a tem-' perature to be measured or regulated, a current responsive device having an operating coil, said device having an element movable in response to coil current, one additional temperature responsive resistor, means for connecting said two resistors and operating coil in series across a substantially constant source of potential, said feeler resistor and additional resistor having respectively positive and negative temperatureresistance coefiicients, said feeler resistor being the only resistor subject to temperature to be measured or regulated with the additional resistor not being subject to a temperature being measured or regulated, a heating coil for said additional resistor, switching means controlled by the movement of said element for disposing said heating coil in a circuit for energizing the same, said heating coil acting upon said additional resistor and providing a calibrated standard temperature for said additional resistor, said two temperature coeificients having such relative magnitudes that under operating conditions the percentage of change of feeler resistance for a given change of feeler temperature is greater than the resulting percentage change of resistance of said additional resistor, said feeler and additional resistor serving to change the current through said coil in an amplified manner.

3. A temperature responsive system for regulating temperature comprising a temperature responsive feeler resistor exposed to the temperature to be regulated, a difierential current responsive device having at least two operating coils and an element movable in response to coil currents, a first additional temperature responsive resistor, means for connecting said feeler resistor and one coil and said first additional resistor in series across a substantially constant source of potential, said feeler resistor and first additional resistor having respectively positive and negative temperature-resistance coefiicients, said feeler resistor being the only resistor subject to temperature to be controlled with the additional resistor not being subject to the temperature being controlled, a second circuit connected across said potential source, said second circuit comprising one temperature responsive resistor in series with the second coil and with a second additional temperature resistor across said potential source, the two temperature resistors in said second circuit having respectively positive and negative temperature-resistance coefllcients, a heating coil for the resistor in the first circuit having the negative temperature coefllcient, a second heating coil for the resistor in the second circuit having the negative temperature coefiicient, switching means controlled by the movement of the movable element or said difierential device for disposing one or the other heating coil in an energizing circuit, the resistor in the second circuit having the positive temperature coefllcient having a predetermined value and bein free 01' the influence of the temperature to be regulated, said heating coils serving to provide calibrated reference temperatures for the resistors having negative coeflicients, the two temperature coeflicients for the resistors in said first circuit having such relative magnitudes and the greater than the resulting percentage change of resistance of the first additional resistor in said first circuit and the percentage change of resistance of the resistor having a positive coefiicient in the second circuit is greater than the resulting percentage change of resistance of the resistor having the negative coefficient in the second circuit, the current in the first circuit varying in an amplified manner due to a variation in feeler resistance.

4. The system according to claim 3 wherein the switching means cooperates with the heating coils so that the movable member oscillates back and forth alternately to energize the heating coils and maintain the entire system in a state of operational oscillation.

5. A temperature responsive system for regulating temperature comprising a temperature responsive feeler resistor exposed to the temperature to be regulated and having a positive temperature resistance coefiicient, a second temperature responsive resistor having a negative temperature resistance coefficient, a differential current responsive device having at least -two operating coils and an element movable in response to coil currents, means for connecting said feeler resistance and said second resistance and one operating coil in series across a substantially constant source of potential, a third temperature responsive resistor having a positive temperature coefficient connected in parallel to said one operating coil, said feeler resistor being the only resistor subject to temperature to be controlled with the additional resistors not being subject to the temperature being controlled, a second circuit connected across said potential source, said second circuit comprising a fourth temperature responsive resistor having a positive temperature coeflicient and a fifth temperature responsive resistor having a negative temperature coefficient and the second operating coil in series with a sixth temperature responsive resistor having a positive temperature coeflicient connected across said second operating coil, a heating coil for the third resistor, a second heating coil for the sixth resistor, switching means controlled by the movement of the movable element of said differential device for disposing one or other heating coil in an energizing circuit, said heating coils serving to provide calibrated reference temperatures for the third and sixth resistors respectively, said feeler resistor and second resistor having such relative magnitudes of temperature coefficients and said fourth and fifth resistors having such relative magnitudes of temperature coeflicients that under operating conditions, the percentage change of feeler resistance to a change in feeler temperature and percentage change of resistance of the fourth resistor are respectively greater than the percentage changes of resistances of the second and fifth resistors, the distribution of current in the operating coils varying in an amplified manner due to variations in value of the various resistors.

R/OBERT AMSLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,517,628 Bottoms Aug. 8, 1950 FOREIGN PATENTS Number Country Date 680,636 France Jan. 22, 1930 

